1. Field of the Invention
The present invention is generally concerned with variable speed drives, for example those adapted to be used on an automobile vehicle for driving from the engine thereof any auxiliary component such as an alternator, water pump, compressor or fan.
2. Description of the Prior Art
As is known, each of the two pulleys that a variable speed drive of this kind comprises, one driving and the other driven, comprises a hub and two annular flange plates in face-to-face relationship to one another around said hub adapted to receive a belt, and at least one of these, hereinafter referred to for convenience as the mobile flange plate, is mounted so as to be mobile axially relative to said hub.
In practice, this mobile flange plate can thus move axially between two extreme positions, one advanced and the other retracted, relative to the other flange plate, hereinafter referred to for convenience as the fixed flange plate, it being understood that when the mobile flange plate of the driving pulley is in the advanced position the mobile flange plate of the driven pulley is in the retracted position and vice versa, the corresponding belt occupying in each case a definite position to which corresponds a specific transmission ratio.
The present invention is more particularly directed to the case where, in order to provide continuous control over the overall configuration and thus the transmission ratio, the mobile flange plate of at least one of the pulleys, the driving pulley, for example, is acted on firstly by elastic return means which continously urge it in the axial direction towards the fixed flange plate and which comprise a variable cone angle annular part of diaphragm which, by means of a peripheral part forming a Belleville spring washer, bears axially on the mobile flange plate through the intermediary of an elastic material annular spacer and a connection piece to which the latter is attached, and which, by means of a central part divided into radial fingers, bears on a part, hereinafter referred to for convenience as the support piece, which is axially fixed with respect to the hub, and secondly by a regulating chamber formed in fluid-tight manner between the mobile flange plate, the diaphragm, the support piece and the hub, and adapted to be connected to an appropriate source of fluid, such as a source of pressurized or depressurized pneumatic fluid.
This is the case, for example, in French patent application No 83 08047 filed May 16, 1983.
In this disclosure, in order to seal the regulating chamber in line with the diaphragm the latter is embedded in a mass of elastic material which, in a particularly advantageous manner, is in continuity with the elastic material spacer through the intermediary of which the diaphragm is supported for tilting on the mobile flange plate and with another elastic material spacer on the other side of said diaphragm through the intermediary of which this diaphragm is similarly supported for tilting on the associated support piece.
In a variable speed drive pulley of this type, in order to preserve the integrity of the sealing of the regulating chamber it is preferable to provide sealing means between the mobile flange plate and the connection piece to which is attached the elastic material spacer through the intermediary of which is provided the tilting support of the diaphragm on the mobile flange plate, whilst ensuring positive axial location of said connection piece and said mobile flange plate relative to one another for the purpose of controlled definition of the cone angle of said diaphragm.
A general object of the present invention is an arrangement constituting a particularly simple and satisfactory way of meeting this requirement.